Method of producing hydrogen cyanide



F. KAEss ETAL METHOD 'oF PRDUCING HYDROGEN CYANIDE Filed Aug. 1, 1955 sept. 29, 1959 United States Patent 'I METHOD oF PironUensIcHYnRoGEN cYANm'Ei Franz KaessF-and Hermann Kronacher;- Tros'tberg; Bernhard Arnolds, Hattingen, `Rurhrg andfWerner Wehrheim,

Bochum, Germany,- assignors to. Suddeutsche Kalkstick The invention.v relates.- to the manufacture of' hydrogenv ture gradation over the length or height of the contact layer. Ther ceramic/tubes. have a relatively -low heat transfer number; in order to attainl the desired temperatures of the catalyst and the gases, it is, therefore necessary ytokeep thewal'ls'of the v'tubes atf a temperature eX- ceeding said-- gas-temperature. This-results frequently in decompositiorrof' thegases,a'nd tliecatalyst` deteriorates 'withformation'of' dust; which; in" turn, causes? uneven conversion-ofthegases s. j.

It is `a principaleobject4 of the invention to providet'a method which prevents" or'reducesk the recited drawbacks andproduces'a uniform conversion ofithe'reatcingfgase's.

`It is-` another vobject of the" invention to provid'efan apparatus suitable" for lcarrying'out the v'process `'of the invention. j

Other objects and advantages will be apparent-from a consideration of "the" speciiicatin 'and' claims. A

According to the invention, the gases are passed through a shaft furnace of rectangular or circular cross section; a plurality of spaced catalyst layers is provided and the gases are heated to the desired reaction temperature of about 500 to 800 C. before they enter each of said layers. In this way, We can adjust the temperature in each of said layers to the concentration and conditions of reaction obtaining in said layers. In front of each layer, viewed in the direction of ow of the gases, a mixing chamber is provided, in which unhomogeneously converted reaction gases of the preceding reaction zone are thoroughly mixed and adjusted to the desired proportions by admixture of fresh gases. The heating zones are provided with thermocouples, which are connected with thermo-regulators for adjusting the temperature.

The invention will be described more in detail with reference to the accompanying drawing, which shows, by way of example, an elevational view of a suitable apparatus.

In the drawing, the reference numeral 1 designates a reactor with three catalyst zones 2, 3, and 4. The catalyst may consist, for example, of alumina. The reaction gases enter the reactor through the conduit 5, pass through the catalyst layers, and leave the reactor through the conduit 6. Before each catalyst zone, a heating zone is provided, which is constituted by a nest of tubes or a channel system, 7, 7, 7". Heating tubes 8, which are preferably of aluminized metal and contain heating resistors, are arranged inside said tubes or channels 7. At least one of said heating zones, or several, or all of them, are

The required reaction tempera-- ture is obtainedr by indirect heating.- vAzserious drawbackof this process hasfbeen-the` dicultyto maintaina-uni form react-ion temperature or a predeterminedtempera-` 2,9%,604 ce Patented-sept. 29, 1959' provided witha` well 9 fora thermocouple, which serves forfcontrollingthe temperature. The catalyst layers 2, 3,;and'1f4 are-carrie'd'by refractorygrids, supported on coluiiiiisi` 1.0i Collectingor mixing chambers 11, 11', 11" 'ar'epr'ovided in. the'path of the gases in front of thegrids, andA gas inlets 152', 12", 12""op'e'nin eachof said chambers. l

. Carbon monoxide containinglgases, which are preferablypreheat'ed in heat exchange with the reactionv gases leaving the reactor, arefpassedinto thereactor throughconduit 5. Said gases ilow through the heating tubes 7 disposed below the layer Z and are heated to a temperature-*above tHe-J-reaction-temperature, forIl instance to a terripera-turefof-"700y to'lOOCt'P" C. Thee-heated carbonv monoxide containing vgases enter the mixing `-chamber 11, into Whichammonia ga'sisy introduced through the inlet 12;""said-a-mmoniais-not preheated, orit isheated only tof a relativelylow"temperature offabout- 3`00-to 600 C. In the' m ing'chamber 113' abouti 1` partby volumel of the ammonia/gas: lismix'edwith about 2to`10parts by vol'unif'; of-*thee preheated-carbonmonoxide containing gassfand-themixture assumesy the required reaction temperature Thelgas mixture-enters then the catalyst layer-, islreactetdtherein, and after leaving said layer, The

reacting gases changes in the subsequent reaction zones and highertemperatures-are required-for obtaining equilibriurnffV j Even under the conditions set forth above, it 'may happenthat ceramic. heatingqtub'es are-#destroyed The use of. metallicV tubes increases theloss' of reactants,` particularly ofcarbon-jmonoxide, even though high qualityalloys are employed. Unexpectedly, it wasfound vthat' theV decclnmpisi-tionklv of the-gasesf -could 'be prevented or cons iderably. `reduced when the metallic tubesfwerealurn'iniged-f .'l`l.1e refo` re.k theceramie t-.ubesy may be replacedv by metallic tubes, provided the latter are completely and carefully aluminized.

From the foregoing description, it will be readily seen that our novel method allows of maintaining a uniform reaction temperature in the catalyst layers, as well as of providing a differentiated gradation of the temperature in the various layers. The division of the total catalyst space into several spaced layers reduces the formation of dust and irregular conversion of the gases. As the ammonia is brought to reaction temperature only by admixture to the higher heated carbon monoxide containing gases, the risk of decomposition of the ammonia is reduced. Our method allows of obtaining an approximately theoretic conversion of the gases to hydrogen cyanide with a minimum of losses.

The following examples illustrate a way in which the invention may be practiced, but are not to be construed as limiting its scope. All parts are given by volume, unless specified otherwise.

Example 1 A reactor as shown in the drawing contained three catalyst layers, each of 50 ltrs. of alumina gel. 100 cu. m. per hour of carbon monoxide, preheated to 550 C., were introduced through conduit 5 and heated in the heating tubes 8 to 750 C.; gaseous ammonia of a temperature of 350 C. was introduced through inlet 12 into the mixing chamber 11 in the amount required to obtain a gas mixture consisting of 5 parts of CO and l part of NH3; said gas mixture had a temperature of about 650- 660 C. After leaving the catalyst zone 2, the gas mixture contained 6.8 percent of HCN and had a temperature of 600 C. Presently, the gas mixture was heated in the heating Vzone 7 to a temperature of 700 C.V and mixed in the mixing chamber 11 with 0.5 part of ammonia having a temperature of 350 C. Said gas mixture, 4when leaving the catalyst 3, contained 7.7% of HCN. It was heated in the heating zone 7 again to 700 C. and further 0.5, part of NH3 were added through conduit 12". The end product leaving the catalyst 4 had a temperature of 620 C. and contained 8.5% of HCN. Less than 1 percent of the introduced ammonia had been decomposed to nitrogen and hydrogen.

Example 2 In the same reactor, 100 cu. m. per hour of CO having a temperature of 750 C. were mixed in the mixing chamber 11 withrammonia of 350 C. to a mixture having a temperature of 600 C. and consisting of 2.5 parts of CO and 1 part ofk NH3. The gases leaving the catalyst Z had a temperature of about 560 C. and were heated in 7' to 620 C.; on leaving catalyst 3 the gases had a temperature of about 590 C., and they were heated in the heating zone 7 to 650 C. The gases leaving the catalyst 4 had a temperature of about 610 C. and con-4 tained 8.3 percent of HCN. The total NH3 loss by decomposition was about 1.5 percent, calculated on the input of NH3.

Example 3 In order to show the advantages of our novel method, a reactor similar to the reactor shown in the drawing was used, which had however a single catalyst layer corresponding in amount to the three spaced layers of the preceding examples, and a single preheating and mixing zone.

In this case, 100 cu.V m. of carbon monoxide per hour had to be preheated to 900 C. and were mixed with NH3 580 C. and they contained 7.1% of HCN. The ammonia loss by decomposition was in this case 12 percent:

While we prefer to use three spaced catalyst layers with corresponding preheating and mixing zones, it will be obvious that also two or four, or more of such layers may be arranged in the manner described, and that other modifications may be resorted to without departing from the spirit of the invention.

We claim:

1. A method for the preparation of hydrogen cyanide comprising heating carbon monoxide to a temperature of about 700 to 1000u C. admixing ammonia of a ternperature of about 300 to 600 C. to said heated carbon monoxide so as to obtain a gas mixture containing carbon monoxide and ammonia in a ratio of about 2 to 10 parts by volume of carbon monoxide to about one part by volume of ammonia, said gas mixture having a temperature within the range of about 500 to 800 C., passing said gas mixture through a first catalyst layer, adding ammonia to the gases leaving said lirst catalyst layer and heating said gases to a temperature within said temperature range but exceeding the temperature in said first catalyst layer, passing said gases through asecond catalyst layer, adding ammonia to the gases leaving said second`catalyst layer and heating said gases to a temperature within said temperature range but exceeding the temperature in said second catalyst layer, and passing said gases through a third catalyst layer.

2. The method as claimed in claim 1 wherein the ratio of carbon monoxide and ammonia in the gas mixture entering the first catalyst layer is at least about 5:1, and wherein about 0.5 part of ammonia is added each time the mixture enters a subsequent catalyst layer.

References Cited in the tile of this patent UNITED STATES PATENTS 

1. A METHOD FOR THE PREPARATION OF HYDROGEN CYANIDE COMPRISING HEATING CARBON MONOXIDE TO A TEMPERATURE OF ABOUT 700 TO 1000*C. ADMIXING AMMONIA OF A TEMPERATURE OF ABOUT 300 TO 600* C. TO SAID HEATED CARBON MONOXIDE SO AS TO OBTAIN A GAS MIXTURE CONTAINING CARBON MONOXIDE AND AMMONIA, IN A RATIO OF ABOUT 2 TO 10 PARTS BY VOLUME OF CARBON MONOXIDE TO ABOUT ONE PART BY VOLUME OF AMMONIA, SAID GAS MIXTURE HAVING A TEMPERATURE WITHIN THE RANGE OF ABOUT 500 TO 800* C., PASS ING SAID GAS MIXTURE THROUGH A FIRST CATALYST LAYER, ADDING AMMONIA TO THE GASES LEAVING SAID FIRST CATALYST LAYER AND HEATING SAID GASES TO A TEMPERATURE WITHIN SAID TEMPERACATALYST LAYER, PASSING SAID GASES THROUGH A SECOND CATALYST LAYER, ADDING AMMONIA TO THE GASES LEAVING SAID SECOND CATALYST LAYER AND HEATING SAID GASES TO A TEMPERATURE WITHIN SAID TEMPERATURE RANGE BUT EXCEEDING THE TEMPERATURE IN SAID SECOND CATALYST LAYER, AND PASSING SAID GASES THROUGH A THIRD CATALYST LAYER. 